Concept
A custom keychain holder for wired earphones, designed in the shape of a mini 50 mm vinyl record. The wire wraps between two discs, similar to string on a yo-yo, and the plug is secured in the center—so your earphones won’t get tangled in your pocket and will always hang from your bag or keys.
The concept rests on three solutions:
• Form and Image. Vinyl is a recognizable symbol of «music you carry with you»; wired headphones are once again perceived as a fashionable accessory, and the holder transforms their storage into part of the overall aesthetic.
• Modular Construction with 4 Parts. Two discs and two central bushings connect without glue or tools. This makes the item repairable—a broken piece can be replaced instead of discarding the entire keychain.
• Color Customization. The buyer selects the color of the discs, the color of the «apple» (the central sticker on the record, depicted by the bushings), and the shape of the carabiner: shell, starfish, or fish. 6 disc colors × 6 bushing colors × 3 carabiner shapes = 108 options from a single set of parts.
All plastic components are 3D-printed, allowing the item to be manufactured in small batches and reprint specific colors on demand.
Target Audience
Materials
Why not injection molding: a mold for 4 parts costs tens of thousands of rubles and only pays for itself with thousands of units. 3D printing is more expensive per piece, but for a batch of 30–100 items, it is ultimately much cheaper and requires no upfront investment before sales begin.
Construction, Dimensions, and Tolerances
The product is assembled from 4 plastic parts and hardware; overall dimensions assembled are Ø 50 × 20 mm, total length with carabiner is about 120 mm, and the weight is approximately 20 g.
Total assembled width calculation: flange 3 + shaft 7 + shaft 7 + flange 3 = 20 mm. The discs seat flush against the flanges on the shafts, leaving a gap of 20 — 3 — 3 — 3 — 3 = 8 mm between them—this is where the wire is wound.
Visualization
Method of Production
Plastic parts are printed using FDM without supports, one color per build plate. A batch of 30 keychains requires approximately 30 hours of one printer’s operation (estimate) and 3–4 hours of manual assembly.
Model Preparation
- Each model component must be created as a separate file (STL or 3MF) according to the dimensions listed in the «Construction» section.
- The grooves on the tracks must be created only on the outer surface of the discs; this is the top surface during printing and will result in the smoothest finish.
- All holes (Ø 12, Ø 3, Ø 6.15, Ø 3.6, Ø 2.5) and the 3×3 recess must be oriented vertically—these parts will not require support structures.
Test Prototypes1. 2–3 sets are printed using PLA to check the form and proportions. 2. Then, 2 sets are printed using PETG to fine-tune clearances: the pin must fit into the socket with resistance, the plug must slide in freely, and the disk must fit onto it by hand. 3. The dimensions from the successful prototype are fixed in the final files and will not be changed thereafter.
Printing a run
Post-processing1. Remove parts from the build plate, trim PETG threads (webbing) and the first layer overlap along the edge 2. Check every bushing with a caliper: 3.5 mm plug into the channel, pin into the control part socket 3. Sort parts by color into labeled containers
